Method and system of coordinating an intensifier and sieve beds

ABSTRACT

A method and system of coordinating an intensifier and sieve beds. At least some of the illustrative embodiments are methods comprising coordinating control of an intensifier with cycles of a sieve bed fluidly coupled to the intensifier such that there is at least one low pressure stroke of the intensifier and at least one high pressure stroke of the intensifier during a fill cycle of the sieve bed.

CROSS-REFERENCE TO RELATED APPLICATIONS

None.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not applicable.

BACKGROUND

Many patients with lung and/or cardiovascular problems may be requiredto breathe therapeutic gas in order to obtain sufficient dissolvedoxygen in their blood stream. So that these patients may be ambulatory,therapeutic gas may be delivered from a portable cylinder. A portablecylinder may, however, provide only limited volume, and thereforeperiodically needs to be refilled. While it is possible to have thesecylinders exchanged or refilled by way of commercial home health careservices, some patients have systems within their homes which generatetherapeutic gas and fill portable cylinders with the therapeutic gas.Systems such as these have come to be known as transfer-fill or“trans-fill” systems. However, the trans-fill systems of the related artfill the portable cylinders very slowly, and are prohibitively expensivefor most patients.

SUMMARY

The problems noted above are solved in large part by a method and systemof coordinating an intensifier and sieve beds. At least some of theillustrative embodiments are methods comprising coordinating control ofan intensifier with cycles of a sieve bed fluidly coupled to theintensifier such that there is at least one low pressure stroke of theintensifier and at least one high pressure stroke of the intensifierduring a fill cycle of the sieve bed.

Other illustrative embodiments are systems comprising a compressor, afirst sieve bed and a second sieve bed which selectively fluidly coupleto the compressor (wherein the first sieve bed produces an enriched gasstream while the second sieve bed purges, and the second sieve bedproduces the enriched gas stream while the first sieve bed purges), andan intensifier with a motive portion and a compressive portion (themotive portion fluidly coupled to the compressor and the compressiveportion fluidly coupled to the enriched gas stream, wherein the motiveportion has a low pressure stroke and a high pressure stroke). Theintensifier is coordinated to begin at least a low pressure stroke and ahigh pressure stroke while the first sieve bed produces the enriched gasstream, and at least a low pressure stroke and a high pressure strokewhile the second sieve bed produces the enriched gas stream.

The disclosed devices and methods comprise a combination of features andadvantages which enable it to overcome the deficiencies of the prior artdevices. The various characteristics described above, as well as otherfeatures, will be readily apparent to those skilled in the art uponreading the following detailed description, and by referring to theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

For a detailed description of the preferred embodiments of theinvention, reference will now be made to the accompanying drawings inwhich:

FIG. 1 illustrates a trans-fill system in accordance with theembodiments of the invention;

FIG. 2A illustrates a timing diagram in accordance with the embodimentsof the invention;

FIG. 2B illustrates a timing diagram in accordance with the embodimentsof the invention; and

FIG. 3 illustrates a flow diagram in accordance with the embodiments ofthe invention.

NOTATION AND NOMENCLATURE

Certain terms are used throughout the following description and claimsto refer to particular system components. This document does not intendto distinguish between components that differ in name but not function.

In the following discussion and in the claims, the terms “including” and“comprising” are used in an open-ended fashion, and thus should beinterpreted to mean “including, but not limited to . . . ”. Also, theterm “couple” or “couples” is intended to mean either an indirect ordirect connection. Thus, if a first device couples to a second device,that connection may be through a direct connection, or through anindirect connection via other devices and connections.

Further, when describing “pressure” in this specification, and in theclaims, the pressure reference shall be to gauge pressure rather thanabsolute pressure.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 illustrates a trans-fill system 1000 for filling portablecylinders in accordance with embodiments of the invention. Devices suchas illustrated in FIG. 1 may be used, for example, in a patient's hometo fill portable oxygen cylinders for ambulatory use. Trans-fill systemsin accordance with embodiments of the invention comprise both electricalcomponents and mechanical components. In order to differentiate betweenelectrical connections and fluid connections, FIG. 1 illustrateselectrical connections between devices with dash-dot-dash lines, andfluid connection, (e.g. tubing connections between devices), with solidlines.

FIG. 1 illustrates that a trans-fill system 1000 in accordance withembodiments of the invention comprise a compressor 10. Compressor 10draws air through inlet 12, compresses the air (in some embodiments toapproximately 30 PSI), and provides the air to other devices of thetrans-fill system 1000, particularly the sieve beds 14 and 16 and theintensifier 18. In accordance with at least some embodiments, compressor10 is an electric motor driven compressor having model number2680CE56-XXX available from Thomas Compressor (A Gardner Denver Product)of Quincy, Ill.

Sieve beds 14 and 16 form at least a part of an oxygen concentrator, andin particular a pressure swing absorption (PSA) system. Each sieve bed14 and 16 is a vessel that is filled in whole or in part with amolecular sieve material, such as OXY-SIEVE 5 available from UOP, LLC ofChicago, Ill. In accordance with some embodiments, each of sieve bed 14and 16 hold approximately 1.5 pounds of molecular sieve material, butgreater or lesser amounts of sieve material may be equivalently used.Consider for purposes of explanation sieve bed 14, with theunderstanding that the description is equally applicable to sieve bed16. Atmospheric air is forced through the sieve bed 14 by compressor 10.As the air moves through the molecular sieve material, the nitrogen flowis impeded while oxygen and argon move through less impeded. The gasstream exiting the sieve bed 14 has increased oxygen content (e.g., 90%oxygen content or greater), and may be referred to as enriched gas or asan enriched gas stream. Forcing atmospheric air into to the sieve bedmay also be referred to as “filling” the sieve bed, and the period oftime when air is forced through may be referred to as the “fill cycle.”

However, atmospheric air cannot be forced through the sieve bed 14indefinitely as the bed eventually becomes loaded with nitrogen. Thus,generation of the enriched gas stream by the sieve bed 14 isperiodically stopped and the nitrogen trapped in the sieve bed ispurged, such as by venting the sieve bed 14 to atmosphere and/orback-flowing enriched gas. The period of time when a sieve bed is ventedand/or purged maybe referred to as the “purge cycle.” Considering nowboth the sieve beds 14 and 16, while one sieve bed generates theenriched gas stream, the second sieve bed purges, such that at least oneof the sieve beds produces the enriched gas stream at any one time.

Valving system 20 controls the fill cycles and purge cycles of the sievebeds 14 and 16. Valving system 20 may take several forms. In someembodiments, valving system 20 may be a single valve having a pluralityof ports to accomplish the control. In other embodiments, and asillustrated, valving system 20 comprises two valves 22 and 24. In theseembodiments, each valve 22 and 24 is a solenoid operated three-portvalve that selectively fluidly couples one of two ports to a common port(labeled “C” in the drawings, and the arrow direction does not necessaryindicate flow direction). Three-port valves 22 and 24 may be HumphreyMini-Mizers having part number D3061A, available from John Henry FosterCompany of St. Louis Mo. In the valve positions illustrated in FIG. 1,three-port valve 22 fluidly couples the compressor 10 to the sieve bed14, and thus implements the fill cycle of sieve bed 14. Likewise,three-port valve 24 fluidly couples sieve bed 16 to an atmospheric vent,and thus implements the purge cycle of sieve bed 16. At some earlier orlater time, these roles reverse, with three-port valve 22 coupling sievebed 14 to atmospheric vent, and three-port valve 24 coupling compressor10 to sieve bed 16.

The enriched gas stream exiting a sieve bed in the fill cycle flowsthrough a check valve 28, and then to the product tank 26. Likewise,when sieve bed 16 is in the fill cycle, the enriched gas stream passesthrough check valve 30 and then flows to the product tank 26. Althoughcheck valves 28 and 30, and the remaining check valves of the figure,are illustrated to be ball-check valves, any suitable check valve may beequivalently used. The check valves 28 and 30 prevent back flow from theproduct tank through the purging sieve bed. However, in order to assistpurging, a controlled portion of the enriched gas stream is providedfrom the sieve bed in the fill cycle to the sieve bed in the purge cycleby way of a fluid connection through orifice 32. In accordance with atleast some embodiments, the orifice 32 has an aperture diameter ofapproximately 30 thousandths of an inch, a length of approximatelythree-quarters of an inch, and allows enriched gas flow in eitherdirection. The portion of the enriched gas stream flowing from the sievebed in the fill cycle to the sieve bed in the purge cycle aids thepurging by flushing with enriched gas. The trans-fill system 100illustrated in FIG. 1 further comprises a purge valve 34. Much like theorifice 32, the purge valve 34 provides a portion of the enriched gasstream from the sieve bed in the fill cycle to the sieve bed in thepurge cycle, but in accordance with embodiments of the invention thepurge valve 34 operates near the end of the purge cycle to “pre-charge”the sieve bed with enriched gas for the next fill cycle. The time of useof the purge valve 34 is discussed below with respect to FIGS. 2A and2B. In accordance with some embodiments, the purge valve is a two-portsolenoid operated valve, such as Humphrey two-port valves having partnumber D2048 available from the John Henry Foster Company.

In at least some embodiments, compressor 10 generates a compressed airstream having a pressure from approximately 20 PSI to approximately 35PSI. Thus, the enriched gas stream accumulates in the product tank witha pressure of approximately 20 PSI to 35 PSI. However, in order to filla portable cylinder, such as cylinder 36, the pressure of the enrichedgas stream needs to be increased. In order to increase the pressure ofthe enriched gas stream, the trans-fill system 1000 further comprisesthe intensifier 18. The intensifier 18 fluidly couples to the producttank 26 through valve 68. The purpose and operation of valve 68 isdiscussed more below. The intensifier increases the pressure of theenriched gas stream to a pressure sufficient to fill a cylinder. Forexample, if the “full” pressure of cylinder 36 is 2200 PSI, theintensifier 18 generates a peak pressure at its outlet 40 ofapproximately 2700 PSI. Other “full” pressures and peak pressures may beequivalently used.

The term “intensifier” in this specification and in the claims refers toa class of compressor devices that compresses in stages using pistons,and where the motive force for the compression is also supplied by apiston. Thus, the illustrative intensifier 18 has a first stage 42comprising a piston and cylinder, and also has second stage 44comprising a piston and cylinder. The first stage 42 and the secondstage 44 form the compression or compressive portion of the intensifier.The motive force for the compression comes from a motive portion 46comprising a piston and cylinder coupled to the first stage 42 and thesecond stage 44 by way of a shaft 48. In the orientation of FIG. 1, asthe first stage 42 piston shuttles right, the piston draws low pressureenriched gas from the product tank 26. The motive portion 46 then forcessecond stage 44 piston to shuttle left, which compresses the enrichedgas in the first stage 42 and draws the partially compressed enrichedgas to the second stage 44. As the second stage 44 compresses theenriched gas to produce a high pressure enriched gas supplied to thecylinder 36 through a cylinder fill connector 49, the first stage againdraws enriched gas from the product tank 26. The intensifier 18 may be apart number 200336-1 intensifier produced through Chad Therapeutics,Inc., of Chatsworth, Calif.

As illustrated in FIG. 1, the motive portion 46 of the intensifier 18 ispreferably driven by compressed air supplied by the compressor 10.Valving system 50 controls the shuttling of the intensifier 18, and maytake several forms. In some embodiments, valving system 50 may be asingle valve having a plurality of ports to appropriately apply thecompressed air to accomplish the shuttling of the intensifier. In otherembodiments, and as illustrated, valving system 50 comprises two valves52 and 54. In these embodiments, each valve 52 and 54 is a solenoidoperated three-port valve that selectively fluidly couples one of twoports to a common port (labeled “C” in the drawings, and the arrow doesnot necessarily indicate flow direction). Like three-port valves 22 and24, three-port valves 52 and 54 may be Humphrey Mini-Mizers availablefrom John Henry Foster Company. In the valve positions illustrated inFIG. 1, three-port valve 52 fluidly couples the compressor 10 to motiveportion 46 to perform the high pressure stroke of the second stage 44,and simultaneously valve 54 vents its side of the motive portion 46.Thereafter, three-port valve 54 fluidly couples the compressor 10 tomotive portion 46 to perform the low pressure stroke of the first stage42, and simultaneously three-port valve 54 vents its side of the motiveportion 46. In some embodiments, the shuttling of the intensifier 18 iscoordinated to the fill cycle and purge cycle of the sieve beds 14 and16.

Trans-fill system 1000 in accordance with embodiments of the inventionalso comprises a processor 56. The processor 56 may be amicrocontroller, and therefore the microcontroller may be integral withread only memory (ROM) 58, random access memory (RAM) 60, a digitaloutput (DO) module 62 and an analog-to-digital (A/D) converter 66. Inalternative embodiments the processor 56 may be implemented as astandalone central processing unit in combination with individual ROM,RAM, DO and A/D devices.

The ROM 58 stores instructions executable by the processor 54. Inparticular, the ROM 58 comprises software programs that coordinatecontrol of the sieve beds and intensifier by controlling the varioustwo-port and three-port valves in the trans-fill system 1000. The RAM 60is the working memory for the processor 56, where data is temporarilystored, and from which instructions are executed. Processor 54 couplesto other devices within the trans-fill system by way of the digitaloutput module 62 and A/D module 66. In particular, the processor 54electrically couples to and controls three-port valves 22 and 24 of thevalving system 20, and valves 52 and 54 of the valving system 50, by wayof digital output module 62. Processor 56 also electrically couples andcontrols three-port valve 68, as well as two-port valves 34 and 70, byway of the digital output module 62. Finally with respect to the digitaloutput module 62, the processor couples to and implements on/off controloff the compressor 10.

A trans-fill system 1000 in accordance with at least some embodiments ofthe invention also has a plurality of analog signals of interest withinthe system, and thus the processor couples to devices creating analogsignals by way of the A/D converter 66. In particular, processor 56 maycouple to a pressure transducer 72 and a gas analyzer 74 by way of theA/D converter. Gas analyzer 74 fluidly couples to and samples theenriched gas stream as it exits the product tank 26, but the enrichedgas stream may be equivalently sampled at other locations as well. Thegas analyzer 74 determines the oxygen content of the enriched gas. Thegas analyzer 74 may be, for example, an oxygen-selective sensor suchsensors based on zirconium oxide, galvanic, or paramagnetictechnologies. In accordance with embodiments of the invention, if onstart-up of the trans-fill system the oxygen content of the enriched gasstream is below a predetermined threshold (e.g. 90% oxygen), or duringoperation the oxygen content falls below the predetermined threshold,then the enriched gas stream is preferably not provided to cylinder 36.

At initial start-up of the trans-fill system 1000, it may take severalfill cycles and purge cycles of the sieve beds 14 and 16 before theenriched gas stream meets or exceeds the predetermined threshold ofoxygen concentration. In some configurations, the sieve beds 14 and 16may need to be operational for three to five minutes before the enrichedgas meets or exceeds the threshold. Likewise during operation, when theoxygen content drops, the sieve beds 14 and 16 may need to beoperational for several fill cycles and purge cycles before the enrichedgas oxygen content again meets or exceeds the predetermined threshold.In order not to provide the enriched gas below the predeterminedthreshold to the cylinder 36, when the enriched gas oxygen content fallsbelow the predetermined threshold, the enriched gas stream is blockedfrom the intensifier 18 by way of valve 68 under control of theprocessor 56. However, there are several considerations when ceasing theenriched gas flow, such as what to do with the substandard enriched gasstream, and how to handle operation of the intensifier 18 when theenriched gas stream is blocked. The latter is addressed first.

Still referring to FIG. 1, illustrative trans-fill system 1000 usescompressor 10 to supply compressed air both the sieve beds 14 and 16,and as the driving force of the motive portion 46 of the intensifier 18.Thus, compressor 10 has sufficient capacity to supply both the sievebeds and the intensifier; however, if the compressed air produced is notconsumed, the compressor 10 tends to over-pressure, which may causeactivation of pressure relief valves of the compressor 10. In order toavoid this situation, and in accordance with embodiments of theinvention, the intensifier 18 continues to operate even in the absenceof the enriched gas stream being provided to the intensifier. Statedotherwise, the motive portion 46 of the intensifier continues to drawcompressed air from the compressor 10 when the valve 68 blocks flow ofenriched gas from the product tank.

The other consideration when ceasing enriched gas flow to theintensifier 18 is that the sieve beds 14 and 16 still need to generatethe enriched, though substandard, gas stream so that the oxygenconcentration can be improved. Thus, enriched gas in the product tankneeds to be released. Releasing the enriched gas from product tank 26may take many forms. In some embodiments, the product tank 26continuously releases a portion of the enriched gas, such as throughorifice 76. In these embodiments, a portion of the enriched gas isreleased from the product tank at all times. In these embodiments wheregas is released from the product tank 26 continuously, the orifice 76may be selected or adjusted to release approximately 0.5 liters perminute.

Rather than release enriched gas at all times, alternative embodimentsutilize the dump valve 70 and orifice 78. In these embodiments, when theintensifier 18 is not provided the enriched gas stream, the dump valve70, under control of the processor 56, is opened to release thesubstandard enriched gas from the product tank 26. At times when theoxygen content of the enriched gas is above the predetermined threshold,the dump valve 70 closes and valve 68 (in these embodiments operated asa two-port on-off valve, though not specifically illustrated as such)allows the enriched gas stream to flow to the intensifier. In accordancewith the embodiments using dump valve 70, the orifice 78 may be selectedor adjusted to release approximately 2 liter per minute.

Rather than selectively release enriched gas through dump valve 70, orcontinuously release enriched gas through orifice 76, yet still furtheralternative embodiments use three-port valve 68 coupled between theproduct tank 26 and the intensifier 18 for this purpose. In a firstvalve position, the three-port valve supplies the enriched gas stream tothe intensifier 18; however, when the oxygen content of the enriched gasstream drops below the predetermined threshold, the valve 68, undercontrol of the processor 56, changes position and releases thesubstandard enriched gas through orifice 80. In these embodiments, theorifice 80 may be selected or adjusted to release approximately 2 litersper minute.

Still referring to FIG. 1, regardless of the precise embodiments used torelease enriched gas from the product tank, at least some embodimentsrelease the gas inside the case of the trans-fill system 1000. Moreparticularly, in at least some embodiments the released enriched gasflows through tubing 64 that terminates proximate to the air inlet 12 ofthe compressor (e.g., within approximately three inches). In embodimentswhere the compressor 10 comprises an inlet filter, the enriched gas maybe released anywhere inside the housing of the inlet filter. In thisway, the enriched gas released is, in whole or in part, drawn in by thecompressor 10. Re-compressing the substandard but otherwise enrichedgas, and providing that gas to the sieve beds 14 and 16, may shorten theamount of time it takes the sieve beds to reach a state where theenriched gas stream is of sufficient oxygen content, or shorten recoverytime when oxygen content falls below the predetermined threshold. In yetstill further alternative embodiments, the enriched gas released by anyof the mechanisms discussed above may couple to a port accessiblethrough an aperture in the case. Using this port, a home care provideror other interested person may independently verify the oxygen contentusing a separate gas analyzer. In embodiments that release the enrichedgas using the dump valve 70 or the valve 68, the home care provider orinterested person may force a release even when the gas analyzer 74 ofthe trans-fill system 1000 shows the oxygen content to be above thepredetermined threshold and the intensifier is supplied the enrichedgas. For example, the home care provider or other interested person mayforce release by way of the user interface 82.

The discussion now turns to coordination of control of the variouscomponents of the trans-fill system 1000. For purposes of thisdiscussion it is assumed that the valving system 20 comprises twoseparate valves (and thus two independent control signals). Likewise, itis assumed that the valving system 50 comprises two separate valves (andthus two independent control signals). Further, for purposes of thisdiscussion, “on” or “asserted” states of control signals are illustratedas high voltage, and “off” or “de-asserted” states of control signalsare illustrated as low voltage; however, the assignment of assertedstates to voltage levels is merely exemplary, and “asserted” in practicemay equivalently be a low voltage state. Moreover, particular actionsdiscussed as performed in an asserted state may be equivalentlyperformed in a de-asserted state.

FIG. 2A illustrates a timing diagram for control of various componentsof the trans-fill system 1000. During time frame 200, the control signal202 applied to the control valve 22 for sieve bed 14 is asserted,indicating that sieve bed 14 is in the fill cycle. Likewise during timeframe 200, control signal 204 applied to the control valve 24 for sievebed 16 is de-asserted, indicated that sieve bed B is in the purge cycle.After a certain amount of time, in some embodiments approximately sixseconds, the control signal 202 becomes de-asserted while control signal204 becomes asserted. Thus, in time frame 206 sieve bed 14 is in thepurge cycle while sieve bed 16 is in the fill cycle. The pattern ofalternate fill cycle and purge cycle continues during operation of theoxygen concentrator.

FIG. 2A further illustrates control signals 208 and 210 that couple tocontrol valves 52 and 54, respectively. Control valves 52 and 54 controlthe low pressure and high pressure stroke, respectively, of the motiveportion 46 of the intensifier 18. Thus, when control signal 210 isasserted, the motive portion 46 of the intensifier 18 performs the lowpressure stroke, and when control signal 208 is asserted, the motiveportion 46 of the intensifier 18 performs the high pressure stroke. Asillustrated in FIG. 2A, and in accordance with embodiments of theinvention, there is at least one low pressure stroke and one highpressure stroke during a fill cycle/purge cycle (hereinafter, justcycle) of a sieve bed. More particularly, FIG. 2A illustratesembodiments where there are three strokes of motive portion 46 duringeach cycle. Time frame 200 illustrates two low pressure strokes and onehigh pressure stroke, while the contiguous time frame 206 illustratestwo high pressure strokes and one low pressure stroke. Having threestrokes of the motive portion 46 during each cycle is a function of thevolume of sieve beds, the capacity of the compressor 10 and the capacityof the intensifier 18. Holding the capacity of the compressor 10 andintensifier 18 constant, increasing the volume of sieve beds increasesthe possible fill time and therefore the number of strokes of the motiveportion 46 possible during a cycle. Decreasing the volume of sieve bedsdecreases the possible fill time and therefore the number of strokespossible. Holding the amount of sieve material constant, increasing thecapabilities of the compressor 10 and/or intensifier 18 decreases thepossible fill time and therefore the number of strokes of the motiveportion 46 during the cycle. Decreasing the capabilities of thecompressor 10 and/or intensifier 18 increases the possible fill time andtherefore the number of strokes possible.

FIG. 2A further illustrates control signal 212 that couples to purgevalve 34. When control signal 212 is asserted, the purge valve 34 allowsflow of enriched gas between the sieve beds. In accordance withembodiments of the invention, while enriched gas flows between the sievebeds at all times by way of orifice 32, just after the end of a purgecycle of a sieve bed the purge valve 34 is activated to “pre-charge” thepurged sieve bed with enriched gas from the sieve bed that justcompleted the fill cycle. Time frame 200 shows operation of the purgevalve by illustrative pulse 214. Likewise, time frame 206 showsoperation of the purge valve by illustrative pulse 216. In accordancewith at least some embodiments of the invention the purge valve isactive for approximately 100 to 400 milli-seconds. In accordance with atleast some embodiments, both the control signals 202 and 204 for thesieve beds are de-asserted during the period of time that the controlsignal 212 for the purge valve is asserted; however, the granularity ofthe time scale of the illustrative timing diagrams is so large thatthese features are not visible. With respect to cycles where a lowpressure stroke is the last stroke of the cycle, in some embodiments thelow pressure stroke ends substantially simultaneously with the end ofthe fill cycle and the high pressure stroke starts substantiallysimultaneously end of the fill cycle. With respect to cycles where ahigh pressure stroke is the last stroke of the cycle, in someembodiments the high pressure stroke continues after the end of the fillcycle to include the time that the purge valve control signal 212 isasserted. At the end of the purge time, both the high pressure strokecontrol signal 210 and the purge valve control signal 212 arede-asserted, while the low pressure stroke control signal 208 isasserted.

FIG. 2B, plotted on a corresponding “X” or time axis, but on a different“Y” axis, shows an illustrative gas analyzer output signal 218 asfunction of time, and also shows control signal 220 that couples to thecontrol valve 68 and control signal 222 that couples to the dump valve70. In embodiments where the control valve 68 is a three-port valve,when control signal 220 is asserted, control valve 68 fluidly couplesthe intensifier 18 to the sieve beds and/or product tank. When controlsignal 220 is de-asserted, the control valve 68 releases enriched gasfrom the product tank through orifice 80. Dashed line 224 illustrates apoint in time where the oxygen concentration of the enriched gas reachesa predetermined threshold (e.g., 90% oxygen concentration). When thepredetermined threshold is reached, the control signal 220 coupled tothe control valve 68 is asserted, thus fluidly coupling the intensifier18 to the enriched gas stream. FIG. 2B also illustrates, by dashed line226, a point in time where the oxygen concentration falls below thepredetermined threshold. In this situation, the control signal 220coupled to the control valve 68 is de-asserted, thus de-coupling theintensifier 18 from the enriched gas stream and releasing enriched gasthrough orifice 80.

In alternative embodiment where control valve 68 is operated as atwo-port valve and the dump valve 70 is used, when the predeterminedthreshold oxygen concentration is reached (again at the time illustratedby dashed line 224), the control signal 222 coupled to the dump valve 78is de-asserted, thus ceasing the release of the enriched gas from theproduct tank. Simultaneously, the control signal 220 coupled to thecontrol valve 68 is asserted, thus fluidly coupling the enriched gas tothe intensifier 18. When the oxygen concentration falls below thepredetermined threshold (again at the time illustrated by dashed line226), the control signal 222 coupled to the control valve 70 isasserted, thus releasing enriched gas through orifice 78.Simultaneously, the control signal 220 coupled to the control valve 68is de-asserted, thus blocking the flow of enriched gas stream to theintensifier.

Returning now to FIG. 1, trans-fill system 1000 comprises a pressuretransducer 72 fluidly coupled to the cylinder 36 downstream of fillorifice 41. In accordance with at least some embodiments, pressuretransducer 72 may be a part number MLH03KPSP01A pressure transduceravailable from Honeywell of Morris Township N.J. Unlike pressureswitches, which open or close an electrical contact at a predeterminedpressure, a pressure transducer may provide a substantially continuousreading of pressure. The pressure transducer 72 in accordance with atleast some embodiments assists the processor 56 in performing severalfunctions. Firstly, the pressure transducer 72 senses the pressure ofenriched gas within cylinder 36, and when the average pressure readingof the cylinder 36 reaches the “full” pressure (e.g., 2200 PSI), theprocessor 56 turns off the trans-fill system by turning off thecompressor 10.

The second function that the processor 56 performs with the pressurereading provided by the pressure transducer 72 is adjusting the time forthe high pressure stroke of the motive portion 46 of the intensifier 18.In particular, when the cylinder 36 is only partially filled (e.g.,having a bottle pressure less than approximately 1200 PSI), the“dead-head” pressure against which the second stage 44 of theintensifier 18 must work is relatively low. In these situations, thehigh pressure stroke of motive portion 46 may take about the same amountof time as the low pressure stroke. In some embodiments, a fill cycle ofa sieve bed is approximately six seconds, and with three strokes percycle, each stroke takes approximately two seconds. However, as thepressure within the bottle rises (e.g., above 1200 PSI up to the “full”pressure of 2200 PSI), the dead-head pressure against which the secondstage 44 works means that it may take more time to complete the highpressure stroke. In accordance with at least some embodiments of theinvention, the processor 56 monitors the pressure provided by thepressure transducer 72, and adjusts the time for the high pressurestroke of the intensifier 18 based on the pressure. In response, timefor the fill cycle of the sieve bed may be correspondingly increased.For example, in the illustrative embodiments discussed, as the pressurein the bottle increases the time for high pressure stroke may beincreased from two seconds to two and a half seconds. In cycles wherethere is only one high pressure stroke, the cycle time may be increasedfrom six seconds to six and a half seconds. Where there are two highpressure strokes, the cycle time may be increased to seven seconds. Inyet still further embodiments, the time to complete the high pressurestroke may be directly proportional to the bottle pressure. For example,as bottle pressure increase from 1200 PSI to 2200 PSI, the high pressurestroke time may be correspondingly and incrementally increased from twoseconds to two and a half seconds.

In yet still further alternative embodiments, the time allotted to thehigh pressure stroke may be adjusted based on other factors, such as theavailable pressure for the high pressure stroke from the compressor 10.In particular, at times when the compressed air pressure from thecompressor 10 is low (e.g., the very early portions of a fill cycle of asieve bed), the time for the high pressure stroke may be increased tocompensate for the lower motive pressure. These time increases may beindependent of the pressure of cylinder 36. At least some embodimentsattempt to lessen the effect of reduced pressure during the very earlyportions of the fill cycle by implementing an amount of time whereneither sieve bed draws air from the compressor, thus allowing thecompressor time to increase just prior to beginning the next fill cycle.The amount of time where neither sieve bed draws air from the compressormay be on the order of approximately 100 milli-seconds. Allowing thecompressor time to build pressure may also decrease an amount of timeneeded to complete the high pressure stroke of the intensifier, and thusmay delay the time when the high pressure stroke time is increased.

In addition to adjusting the time for the high pressure stroke andturning off the compressor 10 as a function of the pressure of thecylinder 36, the processor 56 may perform other useful functions basedon the pressure read by the pressure transducer 72. For example, whenthe rate of pressure increase is very significant (e.g. the averagepressure arising several hundred PSI in a single high pressure stroke),this may indicate a bad connection between the cylinder 36 and the fillconnector 48. Likewise, if the rate of pressure increase falls to zero,yet the average pressure is below the expected “full” pressure, thetrans-filled device 1000 is most likely being operated at high altitudesand no further pressure is possible. In these situations, the processor56 may stop the compressor 10, and therefore filling of the cylinder 36,as no further pressure may be achievable. Relatedly, if a cylinder 36has been filled but is left coupled to the trans-fill device 1000, itmay over time lose pressure. In accordance with at least someembodiments, when the pressure leaks off to be below a certainpredetermined threshold, the processor 56 may restart the compressor 10and re-fill cylinder 36 to the “full” level.

FIG. 3 illustrates a method in accordance with embodiments of theinvention. In particular, the method may start (block 300) by a userplacing a cylinder 36 in a cylinder fill connector 49. Thereafter, thetrans-fill system generates an enriched gas stream (block 304).Additionally, the intensifier is operated (block 308). The enriched gasstream is tested to determine if the oxygen content is above apredetermined threshold (block 312). If the trans-fill system 1000 hasbeen in a non-operational state for an extended period of time,initially the oxygen content of the enriched gas stream will be belowthe predetermined threshold. Therefore the trans-fill system operatesone or more valves (block 316) to refrain from providing the enrichedgas stream to the intensifier. In some embodiments, only valve 68between the products tank 26 and the intensifier 18 is operated,blocking the flow to the intensifier and also releasing therapeutic gasthrough orifice 80. In alternative embodiments, valve 68 acts only toblock the flow of the enriched gas stream to the intensifier, andadditionally dump valve 70 is operated to allow release of enriched gasto orifice 78. In yet further embodiments, valve 68 operates only toblock the flow enriched gas from the product tank 26 to the intensifier18, and the substandard enriched gas accumulated in the product tank isreleased through orifice 76

Regardless of the precise mechanisms that operates to refrain fromproviding the enriched gas stream to the intensifier and releasingenriched gas from the product tank, the next step is yet anotherdetermination of whether the oxygen content of the enriched gas streamis above the predetermined threshold (block 320). If not, the programloops at this step until the oxygen content of the enriched gas streamrises above the predetermined threshold. In this instance, the one ormore valves are operated (block 324). In embodiments where enriched gasis released by operation of a valve, those valves are operated to ceasethe release of enriched gas and other valves (or possibly the samevalve) are operated to provide the enriched gas stream to theintensifier 18.

Still referring to FIG. 3, thereafter, the cylinder pressure is read(block 328), and the program or method takes two parallel paths. On thefirst path, and in some embodiments, the processor 56 adjusts the highpressure stroke time, and possibly the cycle time, as a function of thecylinder pressure (block 336). The second path is a determination ofwhether the cylinder is full (block 336). If the cylinder is full, theprocess jumps immediately to stopping the compressor (block 340) and theprocess ends (block 344). If, on the other hand, the cylinder is notfull (again block 336), the next step may be determining if the rate ofchange of cylinder pressure is above the predetermined threshold (block348). As discussed above, if the rate of change of the cylinder pressureis above a predetermined threshold, this may indicate that the cylinder36 is not properly coupled to the cylinder fill connector 49, and theonly thing being filled is the tubing between the intensifier 18 and thecylinder fill connector 49. If the rate of change is above thepredetermined threshold, the compressor is stopped (block 340), andagain the process ends (block 344). If, on the other hand, the rate ofchange is below the predetermined threshold, the next step is adetermination whether the rate of change in cylinder pressureapproximately zero (block 352). If the rate of change in cylinderpressure is approximately zero, this may indicate that the trans-fillsystem is being operated at high altitudes and may not be able to reachthe “full” pressure of the cylinder, therefore, the compressor isstopped (block 340), and the process ends (block 344). If, on the otherhand, the rate of change of cylinder pressure is greater than zero, thenprocess retreats to determining whether the oxygen content is above thepredetermined threshold (again block 312).

Using the amount and type of sieve material noted, the compressor andintensifier noted, and the various control strategies noted, atrans-fill system 1000 in accordance with embodiments of the inventionshould be capable of filling a cylinder at or greater than 2 liters perminute when the cylinder pressure is less than approximately 1200 PSI.Further, the trans-fill system 1000 should be capable of filling thecylinder at approximately 1.75 to 2.0 liters per minute when thecylinder pressure is above approximately 1200 PSI.

If the trans-fill system 1000 is used at high altitudes, the fill cycletime may be increased to compensate for slower fill time of the sievebeds 14 and 16 caused by high altitude. Correspondingly, when the fillcycle time is increased, either the time of the various high and lowpressure strokes may increase, or additional strokes may be inserted. Insome embodiments, a user may provide the trans-fill system an altitudevalue of use by way of the user interface 82, and the trans-fill system1000 compensates for altitude based on the altitude value and data fromprior experimentation. In alternative embodiments, the trans-fill system1000 senses pressure at the outlet of the sieve beds, and switchingcycles of the sieve beds 14 and 16 may be based on when pressure at theoutlet of the filling sieve bed reaches a predetermined threshold (e.g.,32 PSI). Not only do the alternative embodiments that sense outletpressure of the sieve beds correct for altitude, but also theseembodiments compensate for lost capacity of the compressor 10 with age.

The above discussion is meant to be illustrative of the principles andvarious embodiments of the present invention. Numerous variations andmodifications will become apparent to those skilled in the art once theabove disclosure is fully appreciated. For example, many of the controlsignals illustrated in FIGS. 2A and 2B are merely logical NOTs of eachother. Thus, a trans-fill system need not have separate digital outputsfor each of these signals; instead, one digital output may be used thecontrol signal logically noted to produce the second signal, or thecontrolled valve may be selected to activate on an opposite assertedstate. This specification discusses cylinders having “full” pressure atapproximately 2200 PSI; however, other “full” pressures, both higher andlower, may be equivalently used. Further, while the various embodimentsare described as implemented in part by a processor 56, the variouscontrols strategies could be equivalently implemented by way of ahardware state machine, and in some cases pneumatically (particularlythe valve control strategies). It is intended that the following claimsbe interpreted to embrace all such variations and modifications.

1. A method comprising: coordinating control of an intensifier withcycles of a sieve bed fluidly coupled to the intensifier such that thereis at least one low pressure stroke of the intensifier and at least onehigh pressure stroke of the intensifier during a fill cycle of the sievebed; monitoring a pressure of a high pressure gas stream created by theintensifier; and adjusting a time for the high pressure stroke of theintensifier based on the pressure of the high pressure gas stream. 2.The method as defined in claim 1, wherein adjusting further compriseslengthening a time for the high pressure stroke directly proportional topressure of the high pressure gas stream.
 3. The method as defined inclaim 1, further comprising adjusting a time for the fill cycle of thesieve bed based on the pressure of the high pressure gas stream.
 4. Themethod as defined in claim 3, wherein adjusting further compriseslengthening the time for the high pressure stroke and lengthening thetime for the fill cycle directly proportional to increasing pressure ofthe high pressure gas stream.
 5. A system comprising: a compressor; afirst sieve bed and a second sieve bed which selectively fluidly coupleto the compressor, wherein the first sieve bed produces an enriched gasstream while the second sieve bed purges, and the second sieve bedproduces the enriched gas stream while the first sieve bed purges; andan intensifier with a motive portion and a compressive portion, themotive portion fluidly coupled to the compressor and the compressiveportion fluidly coupled to the enriched gas stream, wherein the motiveportion has a low pressure stroke and a high pressure stroke, whereinthe intensifier is coordinated to begin at least a low pressure strokeand a high pressure stroke while the first sieve bed produces theenriched gas stream, and at least a low pressure stroke and a highpressure stroke while the second sieve bed produces the enriched gasstream.
 6. The system as defined in claim 5, further comprising: a firstvalve arrangement coupled between the compressor and the first andsecond sieve beds, wherein the first valve arrangement selectivelyfluidly couples the first sieve bed to the compressor and purges thesecond sieve bed and then fluidly couples the second sieve bed to thecompressor and purges the first sieve bed; and a second valvearrangement coupled between the compressor and intensifier motiveportion, wherein the second valve arrangement activates the low pressurestroke and then the high pressure stroke.
 7. The system as defined inclaim 6, further comprising: a processor electrically coupled to thefirst and second valve arrangements; and a pressure transducer fluidlycoupled to a cylinder fill gas stream created by the intensifier;wherein the processor sets a time for the high pressure stroke of theintensifier based the pressure of the cylinder fill gas stream.
 8. Thesystem as defined in claim 7, wherein the processor extends the timewhen the pressure of the cylinder fill gas stream is above apredetermined threshold.
 9. The system as defined in claim 7, whereinthe processor shortens the time when the pressure of the cylinder fillgas stream is below a predetermined threshold.
 10. The system as definedin claim 7, wherein the processor sets the time to be proportional tothe pressure of the cylinder fill gas stream.
 11. The system as definedin claim 5, further comprising: wherein the intensifier is coordinatedto activate a low pressure stroke, then a high pressure stroke, and thenanother low pressure stroke while the first sieve bed produces theenriched gas stream and the second sieve bed purges; and wherein theintensifier is coordinated to activate a high pressure stroke, then alow pressure stroke, and then another high pressure stroke while thesecond sieve bed produces the enriched gas stream and the first sievebed purges.
 12. The system as defined in claim 5, wherein theintensifier produces a cylinder fill gas stream at or greater than 2liters per minute when a pressure of a cylinder being filled is lessthan 1200 PSI, and produces between 1.75 and 2 liters per minute whenthe pressure is greater than 1200 PSI.
 13. A system comprising: meansfor compressing atmospheric air; first and second means for separatingnitrogen from air to create an enriched gas stream, the first and secondmeans for separating fluidly coupled to the means for compressing,wherein the first means for separating produces an enriched gas streamwhile the second means for separating purges, and the second means forseparating produces the enriched gas stream while the first means forseparating purges; means for increasing pressure of the enriched gasstream in at least two stages comprising a low pressure stroke and ahigh pressure stroke, the means for increasing fluidly coupled to theenriched gas stream, and also coupled to the means for compressing,wherein the means for increasing is coordinated to activate at least alow pressure stroke and a high pressure stroke while the first means forseparating the enriched gas stream, and at least a low pressure strokeand a high pressure stroke while the second means for separatingproduces the enriched gas stream; means controlling airflow into andpurge of the means for separating, the means for controlling airflowfluidly coupled to the means for compressing; means for controllingdrive air to the means for increasing pressure, the means forcontrolling drive air fluidly coupled to the means for compressing;means for executing programs and instructions electrically coupled tothe means for controlling airflow and the means for controlling driveair; and means for sensing pressure of a cylinder fill gas streamcreated by the means for increasing, wherein the means for executingsets a time for the high pressure stroke of the mans for increasingbased the pressure of the cylinder fill gas stream.